Trucks and in particular long haul trucks use large volumes of diesel fuel in transporting goods. As the price of diesel increases, the cost of freighting goods also increases. While at least part of the increase in costs is passed on to the end consumer, market forces have caused the truck operator to absorb much of the additional costs thereby reducing their profit margin. Consequently alternative fuel sources have been investigated.
LPG (Liquid Petroleum Gas) has been used as an alternative fuel source for diesel engines. While LPG is stored under pressure (approximately 150 psi) in the tank which maintains the LPG in a liquid state, LPG is usually used in a gaseous state at pressures well below 140 psi which is the pressure required to maintain LPG in a liquid state.
LPG has also been used with diesel in dual fuel systems. In US2005205021 a separate set of injectors introduce gaseous LPG into the combustion chamber, whereas in U.S. Pat. No. 5,408,957, U.S. Pat. No. 4,520,766, JP1318755 and GB1252458, gaseous LPG is mixed with air prior to introducing the air mixture to the combustion chamber.
The problem with using LPG as the sole fuel source for diesel engines is that the engines need substantial modification to overcome the reduction in lubricity with the use of LPG and the ability to provide the combustion of the LPG. Modification of engines is a major expense and voids the warranties from the engine manufacturer. Even with LPG and diesel dual fuel systems, diesel engines need to be modified to allow the introduction of LPG into the combustion chamber.